Device for the axial retention of a dental instrument extremity having an axis crossed by at least one locking pin

Abstract

The invention relates to a device for axial retention of a dental instrument shank and for transmitting the rotational driving of the instrument. The device is arranged in a head of a contra-angle or handpiece. The shank has an annular groove in which at least one stud is able to engage radially, and a flat permitting rotational driving of the shank. The rotational movement is communicated by an output pinion of a mechanical transmission assembly coupled to a drive motor and arranged in a sleeve joined to the head of the contra-angle. The device is formed by a shaft traversed axially by the instrument shank, at least one elastic lever, and at least one pin. There is cooperation of the pin or pins with the flat provided on the instrument shank.

1 . Device for axial retention of a dental instrument shank and for transmitting rotational driving of the dental instrument, being arranged in a head of a contra-angle or handpiece, the shank having an annular groove at an end thereof, the groove being engaged radially by at least one stud and permitting a flat to rotationally drive the shank, rotational movement being communicated to the instrument by an output pinion of a mechanical transmission assembly coupled to a drive motor and arranged in a sleeve joined to the head of the contra-angle or of the handpiece, said device comprising:
 a shaft traversed axially by the instrument shank;   at least one elastic lever manufactured independently from the shaft and arranged axially in an outer seat of said shaft, each lever bearing a stud; and   at least one pin, arranged in a transverse hole in an upper part of the shaft and offset laterally with respect to the axial direction of the shaft, the pin being cooperative with the flat provided on the instrument shank, said shaft having a seat extending longitudinally on the shaft and comprising a bottom extended from an arm-fixing means in a direction of the annular groove.   
     
     
         2 . Device according to  claim 1 , wherein said shaft has a general cylindrical shape and a greater diameter in a central part thereof than a diameter at either of the two ends,
 forming a shoulder above, serving as a lower axial abutment for a pinion engaged axially on the upper part of the shaft,   and a shoulder below serving as an upper axial abutment for a ball bearing.   
     
     
         3 . Device according to  claim 2 , wherein each pin has a length smaller than or at most substantially equal to a diameter of an upper part of the shaft engagement of the pinion on the upper part of the shaft blocking the pin in said shaft. 
     
     
         4 . Device according to  claim 1 , further comprising:
 a lever being blocked in a lower part between a shoulder of the shaft and an inner ring of a ball bearing of the head, the upper part of the lever having a degree of freedom in a radial direction with respect to the instrument shank, and comprising a stud engaging the annular groove of the shank.